JP7264266B2 - secondary battery - Google Patents

Description

The present technology relates to secondary batteries.

Due to the widespread use of various electronic devices such as mobile phones, secondary batteries are being developed as power sources that are compact and lightweight and can provide high energy density. Since the configuration of a secondary battery affects battery characteristics, various studies have been made on the configuration of the secondary battery.

Specifically, in order to obtain good productivity and the like, an electrode group is housed inside a positive electrode case and a negative electrode case facing each other, and all of the plurality of positive electrode tabs are gathered in the positive electrode case above the electrode group. All of the plurality of negative electrode tabs are current-collected to the negative electrode case below the electrode group (see Patent Documents 1 and 2, for example). Further, in order to prevent variations in gaps between the electrode bodies (positive electrode and negative electrode), the electrode bodies are housed inside the positive electrode can and the negative electrode can facing each other, and all of the plurality of positive electrode leads are placed in the electrode body. and all of the plurality of negative leads are collected on the side of the electrode body opposite to the plurality of positive leads (see, for example, Patent Document 3).

JP 2011-141997 A Japanese Patent Application Laid-Open No. 2010-212206 JP 2013-187182 A

Various studies have been made to solve the problems of secondary batteries, but the energy density per unit volume of the secondary batteries is still insufficient, so there is still room for improvement.

The present technology has been made in view of such problems, and an object thereof is to provide a secondary battery capable of increasing the energy density per unit volume.

A secondary battery according to an embodiment of the present technology includes a power generation element including a plurality of electrodes stacked with each other in a stacking direction with separators interposed therebetween, and each of the plurality of electrodes is led out in a first direction that intersects the stacking direction. each end of the plurality of current collectors led out in the first direction includes a first bent portion bent in a second direction intersecting the first direction, the first bent are in contact with each other while overlapping each other in the second direction, and at least one of the plurality of first curved portions terminates in the middle of the end surface of the power generation element in the second direction. It is.

According to the secondary battery of one embodiment of the present technology, each of the plurality of electrodes stacked with the separator interposed therebetween includes a current collector led out in the first direction, and the plurality of electrodes led out in the first direction Each of the current collectors includes a first bent portion bent in the second direction, the first bent portion is in contact with the adjacent first bent portion in the second direction while overlapping, and the plurality of the first bent portions are in contact with each other. Since at least one of the one bent portions terminates in the middle of the end face in the second direction of the power generation element, the energy density per unit volume can be increased.

Note that the effects of the present technology are not necessarily limited to the effects described here, and may be any of a series of effects related to the present technology described below.

It is a sectional view showing composition of a secondary battery in a 1st embodiment of this art. FIG. 2 is a perspective view showing the configuration of the main part of the secondary battery shown in FIG. 1; 2 is an enlarged cross-sectional view showing the configuration of the main part of the secondary battery shown in FIG. 1; FIG. 2 is another cross-sectional view showing an enlarged configuration of the main part of the secondary battery shown in FIG. 1. FIG. FIG. 4 is a cross-sectional view for explaining a manufacturing process of a secondary battery; FIG. 10 is another cross-sectional view for explaining the manufacturing process of the secondary battery; FIG. 3 is a cross-sectional view for explaining the configuration of a secondary battery of a comparative example; FIG. 5 is another cross-sectional view for explaining the configuration of a secondary battery of a comparative example; It is a perspective view showing composition of a secondary battery in a 2nd embodiment of this art. FIG. 10 is a cross-sectional view showing the configuration of the main part of the secondary battery shown in FIG. 9; FIG. 10 is another cross-sectional view showing the configuration of the main part of the secondary battery shown in FIG. 9; 3 is a perspective view showing the configuration of a secondary battery of Modification 1. FIG. 10 is a cross-sectional view showing the configuration of a secondary battery of Modification 2. FIG. FIG. 11 is a perspective view showing the configuration of a secondary battery of modification 2; FIG. 11 is a cross-sectional view showing the configuration of a secondary battery of Modification 3; FIG. 11 is a cross-sectional view showing the configuration of a secondary battery of Modification 4; 10 is a perspective view showing the configuration of a secondary battery of modification 4. FIG.

Hereinafter, one embodiment of the present technology will be described in detail with reference to the drawings. The order of explanation is as follows.

1. Secondary battery (first embodiment)
1-1. Overall configuration 1-2. Configuration of main part 1-3. Operation 1-4. Manufacturing method 1-5. Action and effect 2 . Secondary battery (second embodiment)
2-1. Configuration 2-2. Operation 2-3. Manufacturing method 2-4. Action and effect 3. 4. Comparison of element space volume. Modification

<1. Secondary Battery (First Embodiment)>
First, the secondary battery of the first embodiment of the present technology will be described.

The secondary battery described here is a secondary battery having a flat and columnar shape, and includes so-called coin-shaped secondary batteries, button-shaped secondary batteries, and the like. This flat and columnar secondary battery has a pair of bottoms facing each other and sidewalls between the pair of bottoms, as will be described later. is getting smaller.

The charge/discharge principle of the secondary battery is not particularly limited. A secondary battery in which a battery capacity is obtained by utilizing absorption and release of an electrode reactant will be described below. This secondary battery includes an electrolyte together with a positive electrode and a negative electrode. In the secondary battery, in order to prevent electrode reactants from depositing on the surface of the negative electrode during charging, the charge capacity of the negative electrode is greater than that of the positive electrode. larger than the discharge capacity. That is, the electrochemical capacity per unit area of the negative electrode is set to be larger than the electrochemical capacity per unit area of the positive electrode.

The type of electrode reactant is not particularly limited, but light metals such as alkali metals and alkaline earth metals. Alkali metals include lithium, sodium and potassium, and alkaline earth metals include beryllium, magnesium and calcium.

In the following, the case where the electrode reactant is lithium will be taken as an example. A secondary battery whose battery capacity is obtained by utilizing the absorption and release of lithium is a so-called lithium ion secondary battery. In this lithium ion secondary battery, lithium is intercalated and deintercalated in an ionic state.

<1-1. Overall configuration>
FIG. 1 shows a cross-sectional structure of a secondary battery, and FIG. 2 shows a perspective structure of main parts of the secondary battery shown in FIG. However, FIG. 2 shows the battery element 20, the positive electrode tab 30, and the negative electrode tab 40, which will be described later, as main parts of the secondary battery, and the positive electrode tab 30 and the negative electrode tab 40 are separated from the battery element 20. is shown.

Hereinafter, for convenience, the upper, lower, right, and left directions in FIGS. 1 and 2 are referred to as the upper, lower, right, and left directions of the secondary battery. Also, the direction (vertical direction) in which the positive electrode 21, the negative electrode 22, and the separator 23, which will be described later, are stacked is referred to as a stacking direction S.

Since this secondary battery is a button type secondary battery, as shown in FIG. Here, the secondary battery has a flat and cylindrical (columnar) three-dimensional shape. The dimensions of the secondary battery are not particularly limited, but for example, the outer diameter (diameter here) D=3 mm to 30 mm and the height H=0.5 mm to 70 mm. However, the ratio of the outer diameter D to the height H (D/H) is greater than 1 and 25 or less.

Specifically, the secondary battery includes a battery can 10, a battery element 20, a positive electrode tab 30, a negative electrode tab 40, and a gasket 50, as shown in FIGS.

[Battery can]
The battery can 10 is, as shown in FIG. 1, a flat and columnar exterior member that houses the battery element 20 . The battery can 10 has a three-dimensional shape that is flat and cylindrical in accordance with the three-dimensional shape of the secondary battery described above. Therefore, the battery can 10 has a pair of bottom portions N1 and N2 and a side wall portion N3. The side wall portion N3 has one end connected to the bottom portion N1 and the other end connected to the bottom portion N2. As described above, since the battery can 10 is cylindrical, each of the bottom portions N1 and N2 has a circular planar shape, and the surface of the side wall portion N3 is a convex curved surface.

Here, battery can 10 includes outer can 11 and outer cup 12 .

The outer can 11 has a hollow, flat, cylindrical three-dimensional shape with one end open and the other end closed, and is a so-called vessel-like first outer package. Since the outer can 11 includes a bottom portion 11M and a side wall portion 11W, it has an opening portion 11K. Moreover, the outer can 11 accommodates the battery element 20 inside.

The exterior cup 12, like the exterior can 11, has a hollow, flat, cylindrical three-dimensional shape with one end open and the other end closed, and is a so-called container-like third shape. 2 exterior. The exterior cup 12 includes a bottom portion 12M and side wall portions 12W and thus has an opening 12K. In addition, since the exterior cup 12 faces the exterior can 11 with the battery element 20 interposed therebetween in the stacking direction S, the exterior cup 12 seals the opening 11K of the exterior can 11 .

In the battery can 10, the battery element 20 is housed inside the outer can 11, and the outer can 11 and the outer cup 12 are arranged so that the openings 11K and 12K face each other, and the bottom 12M is open. The outer can 11 and the outer cup 12 are fitted together so that the portion 11K is shielded and the side wall portion 12W overlaps the side wall portion 11W from the outside. Since the side wall portion 12W is crimped to the side wall portion 11W via the gasket 50, a so-called crimped portion C (crimped portion) is formed. Since the battery can 10 (outer can 11 and outer cup 12 ) is sealed using the crimp portion C, the battery element 20 is sealed inside the battery can 10 . That is, the battery can 10 described here is a so-called crimp-type battery can. However, in FIG. 1, the illustration of the crimp portion C (crimping structure) is simplified.

The outer can 11 is conductive and has one of a positive polarity and a negative polarity, and the outer cup 12 is conductive and has a positive polarity and a negative polarity. have the other of the polarities. Here, since the outer can 11 is connected to the positive electrode 21 of the battery element 20 described later via the positive electrode tab 30, it functions as a positive electrode terminal for external connection of the secondary battery. Moreover, since the outer cup 12 is connected to the negative electrode 22 of the battery element 20 to be described later via the negative electrode tab 40, it functions as a negative electrode terminal for external connection of the secondary battery. As a result, the outer can 11 has a positive polarity and the outer cup 12 has a negative polarity opposite to the polarity of the outer can 11 .

The outer can 11 contains one or more of conductive materials such as metals (including stainless steel) and alloys in order to function as a positive electrode terminal. Here, the outer can 11 contains one or more of aluminum, an aluminum alloy, stainless steel, and the like.

The outer cup 12 contains one or more of conductive materials such as metals (including stainless steel) and alloys in order to function as a negative electrode terminal. Here, the exterior cup 12 contains one or more of iron, copper, nickel, stainless steel, iron alloys, copper alloys, nickel alloys, and the like. The type of stainless steel is not particularly limited, but includes SUS304 and SUS316.

However, the outer can 11 (side wall portion 11W) and the outer cup 12 (side wall portion 12W) are electrically separated (insulated) from each other via the gasket 50 .

[Battery element]
The battery element 20, as shown in FIGS. 1 and 2, is a power generating element that advances charge-discharge reactions, and includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolytic solution that is a liquid electrolyte. there is However, illustration of the electrolytic solution is omitted in FIG.

Note that FIG. 2 also shows a laminate 120 used for producing the battery element 20 in the manufacturing process of the secondary battery, which will be described later. This laminate 120 has the same structure as the battery element 20 except that the positive electrode 21, the negative electrode 22 and the separator 23 are not impregnated with the electrolytic solution.

This battery element 20 has a three-dimensional shape corresponding to the three-dimensional shape of the battery can 10 . The “three-dimensional shape corresponding to the three-dimensional shape of the battery can 10 ” means a three-dimensional shape substantially similar to the three-dimensional shape of the battery can 10 . Compared to the case where the battery element 20 has a three-dimensional shape different from the three-dimensional shape of the battery can 10, when the battery element 20 is accommodated inside the battery can 10, a so-called dead space (battery This is because a gap between the can 10 and the battery element 20 is less likely to occur. As a result, the internal space of the battery can 10 is effectively utilized, resulting in an increase in the element space volume and an increase in the energy density per unit volume. This “element space volume” is the volume of the internal space of the battery can 10 that can be used to house the battery element 20 .

Here, as described above, since the battery can 10 has a flat and cylindrical three-dimensional shape, the battery element 20 has a flat and substantially cylindrical three-dimensional shape.

In this battery element 20 , a plurality of positive electrodes 21 and a plurality of negative electrodes 22 are stacked with separators 23 interposed therebetween. More specifically, since the plurality of positive electrodes 21 and the plurality of negative electrodes 22 are alternately stacked in the stacking direction S with the separators 23 interposed therebetween, the battery element 20 described here is a so-called stacked electrode assembly. However, each of the uppermost layer and the lowermost layer of the battery element 20 is a separator 23 . The number of layers of the positive electrode 21, the negative electrode 22, and the separator 23 is not particularly limited, and can be set arbitrarily.

Each of the positive electrode 21, the negative electrode 22, and the separator 23 has a substantially circular planar shape with a flat taper. Therefore, the battery element 20 as a whole has a flat and substantially cylindrical three-dimensional shape provided with a flat tapered surface M3T. That is, the battery element 20 has a pair of bottom portions M1 and M2 facing each other, and a side wall portion M3 connected to each of the bottom portions M1 and M2. The surface of the side wall portion M3 includes a curved surface M3C and a tapered surface M3T connected to the curved surface M3C.

Detailed configurations of the positive electrode 21, the negative electrode 22, and the separator 23 will be described later (see FIGS. 3 and 4).

[Positive electrode tab]
The positive electrode tab 30 is electrode wiring for collecting a plurality of positive electrode current collectors 21A (see FIG. 3), which will be described later, and is connected to the plurality of positive electrode current collectors 21A.

Here, positive electrode tab 30 is bent along battery element 20, as shown in FIG. ing. Therefore, the positive electrode tab 30 includes a tab portion 30A and a tab portion 30B connected to the tab portion 30A. The tab portion 30A extends in a direction intersecting the stacking direction S while along the bottom portion M1, and has a planar shape similar to the planar shape of each of the positive electrode 21, the negative electrode 22, and the separator . The tab portion 30B extends in the direction (downward) along the stacking direction S along the side wall portion M3 (tapered surface M3T), and has a strip-like planar shape.

The material for forming the positive electrode tab 30 is the same as the material for forming the positive electrode current collector 21A. However, the material for forming the positive electrode tab 30 may be the same as the material for forming the positive electrode current collector 21A, or may be different from the material for forming the positive electrode current collector 21A.

The connection format of the positive electrode tabs 30 to the plurality of positive electrode current collectors 21A will be described later (see FIG. 3).

[Negative electrode tab]
The negative electrode tab 40 is another electrode wiring for collecting a plurality of negative electrode current collectors 22A (see FIG. 4), which will be described later, and is connected to the plurality of negative electrode current collectors 22A.

Here, the negative electrode tab 40 has the same structure as the positive electrode tab 30 described above. That is, negative electrode tab 40 is bent along battery element 20, as shown in FIG. there is Therefore, the negative electrode tab 40 includes a tab portion 40A and a tab portion 40B connected to the tab portion 40A. The tab portion 40A extends in a direction intersecting the stacking direction S along the bottom portion M2, and has a planar shape similar to the planar shape of each of the positive electrode 21, the negative electrode 22, and the separator . The tab portion 40B extends in a direction (upward direction) along the stacking direction S while along the side wall portion M3 (tapered surface M3T), and has a strip-like planar shape.

The material for forming the negative electrode tab 40 is the same as the material for forming the negative electrode current collector 22A. However, the material for forming the negative electrode tab 40 may be the same as the material for forming the negative electrode current collector 22A, or may be different from the material for forming the negative electrode current collector 22A.

The form of connection of the negative electrode tabs 40 to the plurality of negative electrode current collectors 22A will be described later (see FIG. 4).

[gasket]
The gasket 50 is an insulating member interposed between the outer can 11 (side wall portion 11W) and the outer cup 12 (side wall portion 12W), as shown in FIG. The gap between them is sealed, and the outer can 11 and the outer cup 12 are insulated from each other as described above.

This gasket 50 contains one or more of insulating materials such as polypropylene and polyethylene. The installation range of the gasket 50 is not particularly limited. Here, the installation range of the gasket 50 extends not only to the gap between the side walls 11W and 12W but also to the interior of the battery can 10, that is, the inner surface of the side wall 11W.

[others]
Note that the secondary battery may further include one or more of other components (not shown).

Specifically, the secondary battery has a safety valve mechanism. This safety valve mechanism disconnects the electrical connection between the battery can 10 and the battery element 20 when the internal pressure of the battery can 10 exceeds a certain level due to an internal short circuit, external heating, or the like. The installation position of the safety valve mechanism is not particularly limited. Therefore, the safety valve mechanism may be provided on the outer can 11 or may be provided on the outer cup 12 .

The secondary battery also has an insulator between the battery can 10 and the battery element 20 . This insulator includes one or more of an insulating film, an insulating sheet, and the like, and prevents a short circuit between the outer can 11 and the negative electrode 22 and a short circuit between the outer cup 12 and the positive electrode 21. to prevent Since the installation range of the insulator is not particularly limited, it can be set arbitrarily.

Note that the battery can 10 is provided with an injection hole, an open valve, and the like. The injection hole is sealed after being used to inject the electrolyte into the battery can 10 . As described above, the open valve opens when the internal pressure of the battery can 10 reaches a certain level or higher due to an internal short circuit, external heating, or the like, and releases the internal pressure. The installation positions of the injection hole and the open valve are not particularly limited. Therefore, each of the liquid injection hole and the open valve may be provided in the outer can 11 or may be provided in the outer cup 12 .

<1-2. Configuration of main part>
3 and 4 each show an enlarged cross-sectional configuration of the main part (battery element 20, positive electrode tab 30 and negative electrode tab 40) of the secondary battery shown in FIG.

However, FIG. 3 shows a cross section along the positive electrode tab 30 and FIG. 4 shows a cross section along the negative electrode tab 40 . 3 shows a state in which the positive electrode tab 30 is separated from the battery element 20 in order to make it easier to see the connection form of the positive electrode tab 30, and FIG. 4 makes it easier to see the connection form of the negative electrode tab 40. Therefore, the negative electrode tab 40 is shown separated from the battery element 20 .

The detailed configurations of the positive electrode 21, the negative electrode 22, and the separator 23 will be described below, and then the connection modes of the positive electrode tab 30 and the negative electrode tab 40 will be described. In this case, reference is always made to FIGS. 1 and 2 already described.

[Detailed Configuration of Positive Electrode, Negative Electrode and Separator]
In the battery element 20, which is a laminated electrode body, the plurality of positive electrodes 21 and the plurality of negative electrodes 22 are alternately laminated in the lamination direction S with the separators 23 interposed therebetween, as described above. Thus, the battery element 20 includes a plurality of separators 23 along with a plurality of positive electrodes 21 and a plurality of negative electrodes 22 .

Here, as an example, 6 positive electrodes 21 and 7 negative electrodes 22 are arranged with separators 23 interposed therebetween such that the lowest layer and the uppermost layer of the plurality of positive electrodes 21 and the plurality of negative electrodes 22 are each the negative electrode 22 . alternately stacked. However, the number of laminations of each of the positive electrode 21 and the negative electrode 22 is not particularly limited and can be set arbitrarily.

(positive electrode)
The multiple positive electrodes 21 are multiple electrodes that constitute the battery element 20 . Each of the plurality of positive electrodes 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B, as shown in FIG. Here, the cathode active material layer 21B is provided on both surfaces of the cathode current collector 21A. However, the cathode active material layer 21B may be provided only on one side of the cathode current collector 21A.

The material for forming the positive electrode current collector 21A is the same as the material for forming the outer can 11 . However, the material for forming the positive electrode current collector 21A may be the same as the material for forming the outer can 11 or may be different from the material for forming the outer can 11 . As will be described later, the positive electrode current collector 21A is led out from the positive electrode active material layer 21B.

The positive electrode active material layer 21B contains a positive electrode active material that absorbs and releases lithium, and the positive electrode active material contains one or more of lithium-containing compounds such as lithium-containing transition metal compounds. there is The lithium-containing transition metal compound is an oxide, a phosphoric acid compound, a silicic acid compound, a boric acid compound, or the like, containing lithium and one or more transition metal elements as constituent elements. The positive electrode active material layer 21B may further contain a positive electrode binder, a positive electrode conductor, and the like.

(negative electrode)
The multiple negative electrodes 22 are other multiple electrodes that constitute the battery element 20 . Each of the plurality of negative electrodes 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B, as shown in FIG. Here, the negative electrode active material layer 22B is provided on both surfaces of the negative electrode current collector 22A. However, the negative electrode active material layer 22B may be provided only on one side of the negative electrode current collector 22A.

The material for forming the negative electrode current collector 22A is the same as the material for forming the exterior cup 12 . However, the material for forming the negative electrode current collector 22</b>A may be the same as the material for forming the outer cup 12 or may be different from the material for forming the outer cup 12 . As will be described later, the negative electrode current collector 22A is led out from the negative electrode active material layer 22B. However, the lead-out position of the negative electrode current collector 22A is set so as not to overlap the lead-out position of the positive electrode current collector 21A. ing. This is to prevent a short circuit between the positive electrode current collector 21A and the negative electrode current collector 22A.

The negative electrode active material layer 22B contains a negative electrode active material that absorbs and releases lithium, and the negative electrode active material contains one or more of carbon materials, metal materials, and the like. The carbon material is graphite or the like. A metallic material is a material containing as constituent elements one or more of metallic elements and metalloid elements that form alloys with lithium. Specifically, silicon and tin are constituent elements. contains. This metallic material may be a single substance, an alloy, a compound, or a mixture of two or more thereof. The negative electrode active material layer 22B may further contain a negative electrode binder, a negative electrode conductor, and the like.

(separator)
The separator 23 is an insulating porous film interposed between the positive electrode 21 and the negative electrode 22, and allows lithium to pass through in an ion state while preventing a short circuit between the positive electrode 21 and the negative electrode 22. This separator 23 contains one or more of polymer compounds such as polyethylene.

In addition, the outer diameter of the positive electrode 21 is preferably smaller than the outer diameter of the separator 23 . This is because a short circuit between the positive electrode 21 and the exterior cup 12 is prevented. The height of the negative electrode 22 is preferably smaller than the outer diameter of the separator 23 and larger than the height of the positive electrode 21 . This is because short-circuiting between the negative electrode 22 and the outer can 11 is prevented, and short-circuiting between the positive electrode 21 and the negative electrode 22 due to deposition of lithium during charging and discharging is also prevented.

(Electrolyte)
The electrolyte is impregnated in each of the positive electrode 21, the negative electrode 22 and the separator 23 and contains a solvent and an electrolyte salt. The solvent contains one or more of non-aqueous solvents (organic solvents) such as carbonate compounds, carboxylate compounds and lactone compounds. The electrolyte salt contains one or more of light metal salts such as lithium salts.

[Each connection type of positive electrode tab and negative electrode tab]
Here, as a premise for explaining the configuration of the positive electrode tab 30, the detailed configuration of the positive electrode current collector 21A will be described, and then the connection format of the positive electrode tab 30 will be described. Description in this order also applies to the detailed configuration of the negative electrode current collector 22A and the connection format of the negative electrode tab 40. FIG.

(Detailed Configuration of Positive Electrode Current Collector and Configuration of Positive Electrode Tab)
Since each of the plurality of positive electrodes 21 includes the positive electrode current collector 21A as described above, the battery element 20 includes the plurality of positive electrode current collectors 21A. Here, the lengths of the plurality of positive electrode current collectors 21A are the same as each other.

In each of the plurality of positive electrodes 21, as described above, the positive electrode current collector 21A is led out from the positive electrode active material layer 21B. 1 direction = rightward). Therefore, as shown in FIG. 3, the positive electrode current collector 21A includes a non-lead-out portion 21AX and a lead-out portion 21AY connected to the non-lead-out portion 21AX. The non-leading-out portion 21AX is covered with the positive electrode active material layer 21B, and thus is a portion that is not led out to the outside beyond the positive electrode active material layer 21B. The lead-out portion 21AY is not covered with the positive electrode active material layer 21B, and thus is a portion led out from the positive electrode active material layer 21B.

The end portion of the positive electrode current collector 21A led out in the lead-out direction D211 is bent in a first bending direction D212 (second direction=upward) that intersects the lead-out direction D211. That is, the lead-out portion 21AY led out in the lead-out direction D211 is bent halfway in the first bending direction D212. Here, the lead-out portion 21AY, which is a part of the positive electrode current collector 21A having a positive polarity, is connected to the outer cup 12 having a negative polarity opposite to the positive polarity, that is, the lead-out portion 21AY. It is bent in a direction away from the exterior cup 12 that functions as a negative terminal. Therefore, the first bending direction D212 is the direction from the outer cup 12 toward the outer can 11, that is, the upward direction. This is to prevent a short circuit between the lead-out portion 21AY and the exterior cup 12 .

Since the battery element 20 includes a plurality of positive electrodes 21, each of the plurality of positive electrodes 21 includes a non-lead-out portion 21AX and a lead-out portion 21AY. Thereby, the battery element 20 includes a plurality of lead-out portions 21AY.

Since each of the plurality of lead-out portions 21AY bent in the first bending direction D212 is in contact with the adjacent (front) lead-out portion 21AY in the first bending direction D212 while overlapping, the adjacent lead-out portion 21AY It is connected. Here, the lead-out portion 21AY is joined to the adjacent lead-out portion 21AY using a welding method or the like.

Here, among the plurality of lead-out portions 21AY, some of the lead-out portions 21AY positioned on the rear side in the first bending direction D212 are bent in one step, and therefore, during bending in the first bending direction D212, terminated. That is, part of the lead-out portion 21AY terminates in the middle of the end face (the tapered surface M3T of the side wall portion M3) in the first bending direction D212 of the battery element 20 . As a result, part of the lead-out portion 21AY is bent only in the first bending direction D212, and thus is bent along the battery element 20 (tapered surface M3T).

Some lead-out portions 21AY include a non-bending portion 21AY1 and a first bending portion 21AY2 connected to the non-bending portion 21AY1. The non-bending portion 21AY1 is arranged closer to the positive electrode active material layer 21B than the first bending portion 21AY2, and extends in the lead-out direction D211. The first bent portion 21AY2 is arranged farther from the positive electrode active material layer 21B than the non-bent portion 21AY1, and extends in the first bending direction D212.

The number of lead-out portions 21AY that are bent in one step is not particularly limited, and can be set arbitrarily. That is, the number of partial derivation portions 21AY may be one or may be two or more as long as the number does not correspond to the total number of the plurality of derivation portions 21AY.

Further, the position of the tip of the first bent portion 21AY2 in each of the partial lead-out portions 21AY bent in one step can be arbitrarily set. That is, the positions of the tips of the plurality of first bent portions 21AY2 may be the same or different. Here, the positions of the tips of the plurality of first bending portions 21AY2 are gradually retreated in the direction opposite to the first bending direction D212.

Here, when six positive electrodes 21 and seven negative electrodes 22 are alternately stacked with separators 23 interposed therebetween, three lead-out portions 21AY located on the rear side in the first bending direction D212 are arranged in one step. bent. Further, the position of the tip of the first bent portion 21AY2 of each of the three lead-out portions 21AY gradually recedes in the direction opposite to the first bent direction D212.

On the other hand, among the plurality of lead-out portions 21AY, the remaining lead-out portions 21AY located on the front side in the first bending direction D212 are bent in two stages, and thus bent in the first bending direction D212 and then further led out. It is bent in a second bending direction D213 (third direction=leftward direction) opposite to the direction D211. That is, the remaining lead-out portion 21AY is bent in the first bending direction D212 and then in the second bending direction D213. It is bent along.

As a result, unlike the partial lead-out portion 21AY described above, the remaining lead-out portion 21AY includes the non-bent portion 21AY1 and the first bend portion 21AY2 as well as the second bend portion 21AY3 connected to the first bend portion 21AY2. contains. The second bending portion 21AY3 is arranged farther from the non-bending portion 21AY1 than the first bending portion 21AY2, and extends in the second bending direction D213.

The number of remaining lead-out portions 21AY that are bent in two steps is not particularly limited, and can be set arbitrarily. That is, the number of the remaining derivation units 21AY may be one or may be two or more as long as the number does not correspond to the total number of the plurality of derivation units 21AY.

Further, the position of each tip of the lead-out portion 21AY that is bent in two stages can be arbitrarily set. That is, the positions of the tips of the plurality of second bent portions 21AY3 may be the same or different. Here, the positions of the tips of the plurality of second bending portions 21AY3 are gradually retreated in the direction opposite to the second bending direction D213.

Here, when six positive electrodes 21 and seven negative electrodes 22 are alternately stacked with separators 23 interposed therebetween, three lead-out portions 21AY located on the front side in the first bending direction D212 are arranged in two stages. bent. Further, the position of the tip of the second bending portion 21AY3 among the three lead-out portions 21AY gradually recedes in the direction opposite to the second bending direction D213.

As described above, positive electrode tab 30 includes tab portion 30A along bottom portion M1 and tab portion 30B along side wall portion M3 (tapered surface M3T). Therefore, in the positive electrode tab 30, the tab portion 30A is connected to the remaining lead-out portion 21AY (the second bent portion 21AY3 of the lead-out portions 21AY bent in two stages) among the plurality of lead-out portions 21AY. At the same time, the tab portion 30B is connected to a portion of the plurality of lead-out portions 21AY (the first bent portion 21AY2 of the lead-out portions 21AY bent in one step). In this case, the tab portion 30A is joined to the remaining lead-out portions 21AY by welding or the like, and the tab portion 30B is joined to some of the lead-out portions 21AY by welding or the like. .

The positive electrode tab 30 is connected to the outer can 11 (bottom portion 11M) at the tab portion 30A. Thus, the outer can 11 is connected to the positive electrode 21 (positive current collector 21A) through the positive electrode tab 30 (the tab portion 30A and the tab portion 30B), and thus functions as a positive electrode terminal.

(Detailed configuration of negative electrode current collector and configuration of negative electrode tab)
The negative electrode current collector 22A has a configuration similar to that of the positive electrode current collector 21A described above, and the negative electrode tab 40 has a configuration similar to that of the positive electrode tab 30 described above. Since the connection method (joining method) has already been described, the description thereof will be omitted below.

Since each of the plurality of negative electrodes 22 includes the negative electrode current collector 22A as described above, the battery element 20 includes the plurality of negative electrode current collectors 22A. Here, the lengths of the plurality of negative electrode current collectors 22A are the same as each other.

In each of the plurality of negative electrodes 22, the negative electrode current collector 22A is led out from the negative electrode active material layer 22B as described above. 1 direction = rightward). Therefore, as shown in FIG. 4, the negative electrode current collector 22A includes a non-lead-out portion 22AX and a lead-out portion 22AY connected to the non-lead-out portion 22AX. The non-leading-out portion 22AX is covered with the negative electrode active material layer 22B, and thus is a portion that is not led out to the outside beyond the negative electrode active material layer 22B. The lead-out portion 22AY is not covered with the negative electrode active material layer 22B, and thus is a portion led out from the negative electrode active material layer 22B.

The end of the negative electrode current collector 22A led out in the lead-out direction D221 is bent in a first bending direction D222 (second direction=downward) that intersects the lead-out direction D221. That is, the lead-out portion 22AY led out in the lead-out direction D221 is bent halfway in the first bending direction D222. Here, the lead-out portion 22AY, which is a part of the negative electrode current collector 22A having a negative polarity, is connected to the outer can 11 having a positive polarity opposite to the negative polarity, that is, the lead-out portion 22AY. It is bent in a direction away from the outer can 11 that functions as a positive electrode terminal. Therefore, the first bending direction D222 is the direction from the outer can 11 toward the outer cup 12, that is, downward. This is to prevent a short circuit between the lead-out portion 22AY and the outer can 11 .

Since the battery element 20 includes a plurality of negative electrodes 22, each of the plurality of negative electrodes 22 includes a non-lead-out portion 22AX and a lead-out portion 22AY. Thereby, the battery element 20 includes a plurality of lead-out portions 22AY.

Since each of the plurality of lead-out portions 22AY bent in the first bending direction D222 is in contact with the adjacent (front) lead-out portion 22AY in the first bending direction D222 while overlapping, the adjacent lead-out portion 22AY It is connected.

Here, among the plurality of lead-out portions 22AY, some of the lead-out portions 22AY positioned on the rear side in the first bending direction D222 are bent in one step, and therefore, during bending in the first bending direction D222, terminated. That is, part of the lead-out portion 22AY terminates in the middle of the end face (the tapered surface M3T of the side wall portion M3) in the first bending direction D222 of the battery element 20 . As a result, part of the lead-out portion 22AY is bent only in the first bending direction D222, and is thus bent along the battery element 20 (tapered surface M3T).

Some lead-out portions 22AY include a non-bending portion 22AY1 and a first bending portion 22AY2 connected to the non-bending portion 22AY1. The non-bending portion 22AY1 is arranged closer to the negative electrode active material layer 22B than the first bending portion 22AY2, and extends in the lead-out direction D221. The first curved portion 22AY2 is arranged farther from the negative electrode active material layer 22B than the non-bent portion 22AY1, and extends in the first curved direction D222.

The number of lead-out portions 22AY that are bent in one step is not particularly limited, and can be set arbitrarily. That is, the number of partial derivation portions 22AY may be one or may be two or more as long as the number does not correspond to the total number of the plurality of derivation portions 22AY.

Further, the position of the tip of the first bent portion 22AY2 in each of the partial lead-out portions 22AY bent in one step can be set arbitrarily. That is, the positions of the tips of the plurality of first bent portions 22AY2 may be the same or different. Here, the position of the tip of each of the plurality of first bending portions 22AY2 is gradually retreated in the direction opposite to the first bending direction D222.

Here, when six positive electrodes 21 and seven negative electrodes 22 are alternately stacked with separators 23 interposed therebetween, four lead-out portions 22AY located on the rear side in the first bending direction D222 are arranged in one stage. bent. Further, the position of the tip of the first bending portion 22AY2 of each of the four lead-out portions 22AY gradually recedes in the direction opposite to the first bending direction D222.

On the other hand, among the plurality of lead-out portions 22AY, the remaining lead-out portions 22AY located on the front side in the first bending direction D222 are bent in two stages, and thus bent in the first bending direction D222 and then further led out. It is bent in a second bending direction D223 (third direction=leftward direction) opposite to the direction D221. That is, since the remaining lead-out portion 22AY is bent in the first bending direction D222 and then bent in the second bending direction D223, it is bent along the side wall portion M3 (tapered surface M3T) and then bent to the bottom portion M2. It is bent along.

As a result, unlike the partial lead-out portion 22AY described above, the remaining lead-out portion 22AY includes the non-bent portion 22AY1 and the first bend portion 22AY2, as well as the second bend portion 22AY3 connected to the first bend portion 22AY2. contains. The second bending portion 22AY3 is arranged farther from the non-bending portion 22AY1 than the first bending portion 22AY2, and extends in the second bending direction D223.

The number of remaining lead-out portions 22AY that are bent in two steps is not particularly limited, and can be set arbitrarily. In other words, the number of the remaining derivation portions 22AY may be one, or may be two or more, as long as the number does not correspond to the total number of the plurality of derivation portions 22AY.

Further, the position of each tip of the lead-out portion 22AY that is bent in two stages can be arbitrarily set. That is, the positions of the tips of the plurality of second bent portions 22AY3 may be the same or different. Here, the positions of the tips of the plurality of second bending portions 22AY3 are gradually retreated in the direction opposite to the second bending direction D223.

Here, when six positive electrodes 21 and seven negative electrodes 22 are alternately stacked with separators 23 interposed therebetween, three lead-out portions 22AY located on the front side in the first bending direction D222 are arranged in two stages. bent. Further, the position of the tip of the second bending portion 22AY3 among the three lead-out portions 22AY gradually recedes in the direction opposite to the second bending direction D223.

As described above, the negative electrode tab 40 includes the tab portion 40A along the bottom portion M2 and the tab portion 40B along the side wall portion M3 (tapered surface M3T). Therefore, in the negative electrode tab 40, the tab portion 40A is connected to the remaining lead-out portion 22AY (the second bent portion 22AY3 of the lead-out portions 22AY bent in two stages) among the plurality of lead-out portions 22AY. At the same time, the tab portion 40B is connected to a portion of the plurality of lead-out portions 22AY (the first bent portion 22AY2 of the lead-out portions 22AY bent in one step).

The negative electrode tab 40 is connected to the exterior cup 12 (bottom portion 12M) at the tab portion 40A. Thus, the exterior cup 12 is connected to the negative electrode 22 (negative electrode current collector 22A) via the negative electrode tab 40 (the tab portion 40A and the tab portion 40B), and thus functions as a negative electrode terminal.

Here, as shown in FIG. 2, lead-out portions 21AY and 22AY are arranged adjacent to each other on side wall portion M3 (tapered surface M3T). Therefore, the lead-out direction D211 of the lead-out portion 21AY and the lead-out direction D221 of the lead-out portion 22AY are directions common to each other. That is, the lead-out direction D211 of the lead-out portion 21AY is rightward, and the lead-out direction D221 of the lead-out portion 22AY is also rightward.

<1-3. Operation>
During charging of the secondary battery, lithium is released from the positive electrode 21 in the battery element 20 and absorbed into the negative electrode 22 via the electrolyte. Further, when the secondary battery is discharged, lithium is released from the negative electrode 22 in the battery element 20, and the lithium is absorbed by the positive electrode 21 via the electrolyte. In these cases, lithium is intercalated and deintercalated in an ionic state.

During charging and discharging, the positive electrode tabs 30 are used to collect current from the plurality of positive electrode collectors 21A, and the negative electrode tabs 40 are used to collect current from the plurality of negative electrode collectors 22A.

<1-4. Manufacturing method>
Each of FIGS. 5 and 6 shows a cross-sectional configuration of a secondary battery in the process of being manufactured in order to explain the manufacturing process of the secondary battery. However, FIG. 5 corresponds to FIG. 3 and FIG. 6 corresponds to FIG.

When manufacturing a secondary battery, the secondary battery is assembled according to the procedure described below. In this case, the laminate 120 described above is used to fabricate the battery element 20 . In the following, reference will be made to FIGS. 1 to 4, which have already been described, from time to time.

First, after preparing a slurry containing a positive electrode active material and the like in a solvent such as an organic solvent, the slurry is applied to both surfaces of the positive electrode current collector 21A (the non-leading-out portion 21AX), thereby forming the positive electrode active material layer 21B. Form. As a result, the positive electrode 21 including the positive electrode current collector 21A and the positive electrode active material layer 21B and having the lead-out portion 21AY led out from the positive electrode active material layer 21B is manufactured.

Subsequently, after preparing a slurry containing the negative electrode active material and the like in a solvent such as an organic solvent, the slurry is applied to both surfaces of the negative electrode current collector 22A (the non-leading-out portion 22AX), thereby forming the negative electrode active material layer 22B. Form. As a result, the negative electrode 22 including the negative electrode current collector 22A and the negative electrode active material layer 22B and having the leading portion 22AY led out from the negative electrode active material layer 22B is manufactured.

Subsequently, an electrolyte salt is added to the solvent. An electrolytic solution containing a solvent and an electrolyte salt is thereby prepared.

Subsequently, a laminate 120 is produced by alternately laminating a plurality of positive electrodes 21 and a plurality of negative electrodes 22 with separators 23 interposed therebetween.

Subsequently, each of the plurality of lead-out portions 21AY is bent. In this case, each of the partial lead-out portions 21AY is bent in one step so as to include the non-bent portion 21AY1 and the first bent portion 21AY2, and the second bent portion 21AY2 and the non-bent portion 21AY1 and the first bent portion 21AY2 are bent. Each of the remaining lead-out portions 21AY is bent in two stages so as to include the portion 21AY3. Further, each of the plurality of lead-out portions 21AY is bent so that the lead-out portion 21AY overlaps and contacts the adjacent lead-out portion 21AY in the first bending direction D212.

Also, each of the plurality of lead-out portions 22AY is bent. In this case, each of the partial lead-out portions 22AY is bent in one step so as to include the non-bent portion 22AY1 and the first bent portion 22AY2, and the second bent portion 22AY2 and the non-bent portion 22AY1 and the first bent portion 22AY2 are bent. Each of the remaining lead-out portions 22AY is bent in two steps so as to include the portion 22AY3. Further, each of the plurality of lead-out portions 22AY is bent so that the lead-out portions 22AY overlap and contact the adjacent lead-out portion 22AY in the first bending direction D222.

Subsequently, each of the lead-out portions 21AY is connected to each other, and each of the lead-out portions 22AY is connected to each other. Here, the plurality of lead-out portions 21AY are joined to each other and the plurality of lead-out portions 22AY are joined to each other by using a welding method or the like. This welding method is one or more of a laser welding method, a resistance welding method, and the like. The details of the welding method described here are the same hereinafter.

Subsequently, the positive electrode tab 30 (tab portions 30A, 30B) and the negative electrode tab 40 (tab portions 40A, 40B) are connected to the laminate 120 (the plurality of lead-out portions 21AY, 22AY). Here, each of the positive electrode tab 30 and the negative electrode tab 40 is joined to the laminate 120 using a welding method or the like.

In this case, the tab portion 30A is connected to the remaining derivation portion 21AY (second bent portion 21AY3) that is bent in two stages at the bottom portion M1, and the side wall portion M3 (tapered surface M3T) is bent in one step. The tab portion 30B is connected to a portion of the bent lead-out portion 21AY (first bent portion 21AY2). Further, the tab portion 40A is connected to the remaining lead-out portion 22AY (second bent portion 22AY3) that is bent in two steps at the bottom portion M2, and the side wall portion M3 (tapered surface M3T) is bent in one step. The tab portion 40B is connected to some lead-out portion 22AY (first bent portion 22AY2).

Subsequently, the laminate 120 is accommodated inside the outer can 11 through the opening 11K. In this case, the positive electrode tab 30 (tab portion 30A) is connected to the outer can 11 (bottom portion 11M). Here, the tab portion 30A is joined to the bottom portion 11M using a welding method or the like.

Subsequently, the exterior can 11 and the exterior cup 12 are arranged so that the openings 11K and 12K face each other, and then the exterior cup 12 is fitted to the exterior can 11 with the gasket 50 interposed therebetween. In this case, the bottom portion 12M is used to shield the opening portion 11K, and the side wall portion 12W overlaps the side wall portion 11W from the outside. Also, the negative electrode tab 40 (tab portion 40A) is connected to the exterior cup 12 (bottom portion 12M). Here, the tab portion 40A is joined to the bottom portion 12M using a welding method or the like.

Subsequently, the side walls 11W and 12W are crimped to each other with the gasket 50 interposed therebetween. As a result, the exterior cup 12 is fixed to the exterior can 11 via the gasket 50 , so that the battery can 10 is sealed and the laminate 120 is enclosed inside the battery can 10 .

Finally, after injecting the electrolytic solution into the battery can 10 through an injection hole (not shown), the injection hole is sealed. As a result, the laminate 120 (the positive electrode 21, the negative electrode 22, and the separator 23) is impregnated with the electrolytic solution, so that the battery element 20 is produced. Accordingly, since the battery element 20 is sealed inside the battery can 10, the secondary battery is completed.

<1-5. Action and effect>
According to this secondary battery, the positive electrode current collector 21A (outlet portion 21AY) is led out in the lead-out direction D211 from each of the plurality of positive electrodes 21 stacked with the separator 23 interposed therebetween. Each of the plurality of derived lead-out portions 21AY includes a first bent portion 21AY2 bent in the first bending direction D212. Also, the first bending portion 21AY2 is in contact with the adjacent first bending portion 21AY2 in the first bending direction D212 while overlapping. Furthermore, some of the plurality of first bent portions 21AY2 terminate in the middle of the end face (tapered surface M3T of side wall portion M3) in first bent direction D212 of battery element 20 . Therefore, for reasons explained below, the energy density per unit volume can be increased.

FIG. 7 shows a cross-sectional structure of a secondary battery of a comparative example, and corresponds to FIG. In the secondary battery of this comparative example, as shown in FIG. 7, all of the plurality of lead-out portions 21AY in the positive electrode 21 (positive electrode current collector 21A) are bent in two stages, so that the plurality of first bent portions 21AY2 do not terminate in the middle of bending in the first bending direction D212, that is, all of the plurality of first bending portions 21AY2 are not at the end surface of the battery element 20 in the first bending direction D212 (the tapered surface M3T of the side wall portion M3). ) has the same structure as the secondary battery (FIG. 3) of the present embodiment, except that it is not terminated in the middle. Thus, all of the multiple lead-out portions 21AY include the non-bending portion 21AY1, the first bending portion 21AY2, and the second bending portion 21AY3.

In the secondary battery of the comparative example, since all of the plurality of lead-out portions 21AY are bent in two stages, as shown in FIG. 21AY (first bent portion 21AY2) overlap each other. As a result, the total thickness (maximum thickness) T11 of the first bent portions 21AY2 overlapping each other in the side wall portion M3 is significantly increased. Here, the maximum thickness T11 is the total thickness of each of the six first bent portions 21AY2.

Here, the space occupied by the plurality of first bent portions 21AY2 in the side wall portion M3, that is, the space determined based on the maximum thickness T11 cannot be used to accommodate the battery element 20 inside the battery can 10. space (non-element space).

For these reasons, in the secondary battery of the comparative example, the maximum thickness T11 is significantly increased due to the fact that all of the plurality of first bent portions 21AY2 overlap each other in the side wall portion M3. The volume (non-element space volume) increases. As a result, the volume of the space (element space) that can be used to accommodate the battery element 20 inside the battery can 10 (element space volume) is reduced, making it difficult to increase the energy density per unit volume. .

In contrast, in the secondary battery of the present embodiment, some of the plurality of lead-out portions 21AY are bent in one step, and only the rest are bent in two steps. 2, only part of the lead-out portions 21AY (the first bent portions 21AY2) overlap each other in the side wall portion M3. As a result, the total thickness (maximum thickness) T1 of the first bent portions 21AY2 overlapping each other in the side wall portion M3 is smaller than the maximum thickness T11 in the secondary battery of the comparative example. Here, the maximum thickness T1 is approximately the total thickness of each of the three first bent portions 21AY2.

For these reasons, in the secondary battery of the present embodiment, only some of the plurality of first bent portions 21AY2 overlap each other in the side wall portion M3, resulting in a smaller maximum thickness T1. The non-element space volume is reduced. As a result, the element space volume is increased, so that the energy density per unit volume can be increased.

The actions and effects based on the configuration of the positive electrode 21 described here can be similarly obtained based on the configuration of the negative electrode 22 as well. That is, in the secondary battery of the comparative example shown in FIG. 8, which corresponds to FIG. Become. Therefore, since the non-element space volume increases and the element space volume decreases, the energy density per unit volume also decreases. On the other hand, in the secondary battery of this embodiment shown in FIG. The thickness T2 is smaller than the maximum thickness T12. Therefore, since the non-element space volume decreases and the element space volume increases, the energy density per unit volume increases. Accordingly, in the secondary battery of the present embodiment, similar effects can be obtained in terms of the configuration of the negative electrode 22 as well.

In addition, in the secondary battery of the present embodiment, if the lengths of the plurality of positive electrode current collectors 21A are the same, the electrical resistance of each of the plurality of positive electrodes 21 is made uniform, and the above-described positive electrode Since the wiring structure using the current collector 21A can be easily realized without changing the length of each of the plurality of positive electrode current collectors 21A, a higher effect can be obtained.

The actions and effects based on the configuration of the positive electrode 21 described here can be similarly obtained based on the configuration of the negative electrode 22 as well. That is, if the lengths of the plurality of negative electrode current collectors 22A are the same, the electrical resistance of each of the plurality of negative electrodes 22 is made uniform, and the wiring structure using the negative electrode current collectors 22A is improved. Since it is easily realized, a higher effect can be obtained.

In addition, if the positions of the tips of the plurality of first bending portions 21AY2 that terminate in the middle of bending in the first bending direction D212 gradually recede in the direction opposite to the first bending direction D212, The maximum thickness T1 is less likely to increase as compared with the case where the positions of the tips of the tips match each other. Therefore, since the non-element space volume is less likely to decrease, the element space volume is more likely to increase, so that a higher effect can be obtained.

The actions and effects based on the configuration of the positive electrode 21 described here can be similarly obtained based on the configuration of the negative electrode 22 as well. That is, if the positions of the tips of the plurality of first bending portions 22AY2 that terminate in the middle of bending in the first bending direction D222 gradually recede in the direction opposite to the first bending direction D222, Since the maximum thickness T2 is less likely to increase, a higher effect can be obtained.

Moreover, if a part of the plurality of lead-out portions 21AY further includes the second bent portion 21AY3 bent in the second bent direction D213, the energy density per unit volume is further increased for the reason explained below. Therefore, a higher effect can be obtained.

In the secondary battery of the comparative example (FIG. 7), all of the plurality of lead-out portions 21AY are bent in two stages, so that all the lead-out portions 21AY (second bent portions 21AY3) at the bottom portion M1 of the battery element 20 are mutually bent. overlapping. As a result, the total thickness (maximum thickness T13) of the second bent portions 21AY3 overlapping each other at the bottom portion M1 is remarkably increased, resulting in an increase in the non-element space volume and a decrease in the element space volume. Therefore, the energy density per unit volume is reduced.

In contrast, in the secondary battery of the present embodiment (FIG. 3), some of the plurality of lead-out portions 21AY are bent in one step, and only the rest are bent in two steps. Therefore, only part of the lead-out portions 21AY (the second bent portions 21AY3) overlap each other in the bottom portion M1. As a result, the total thickness (maximum thickness T3) of the second bent portions 21AY3 overlapping each other at the bottom portion M1 is smaller than the maximum thickness T13, so that the element space volume increases due to the decrease in the non-element space volume. do. Therefore, the energy density per unit volume increases.

For these reasons, in the secondary battery of the present embodiment, the energy density per unit volume is further increased not only from the viewpoint of the maximum thickness T1 at the side wall portion M3 but also from the viewpoint of the maximum thickness T3 at the bottom portion M1. Therefore, a higher effect can be obtained.

The actions and effects based on the configuration of the positive electrode 21 described here can be similarly obtained based on the configuration of the negative electrode 22 as well. That is, in the secondary battery of the comparative example (FIG. 7), the plurality of lead-out portions 22AY (second bent portions 22AY3) all overlap each other in the bottom portion M2, so the maximum thickness T14 is significantly increased. In contrast, in the secondary battery of the present embodiment (FIG. 3), only some of the plurality of lead-out portions 22AY (second bent portions 22AY3) overlap each other in the bottom portion M2, so that the maximum thickness T4 is smaller than the maximum thickness T14. Therefore, as the non-element space volume decreases and the element space volume increases, the energy density per volume increases, so that a higher effect can be obtained.

Further, in the secondary battery of the present embodiment, if the positions of the tips of the plurality of second bending portions 21AY3 are gradually retreated in the direction opposite to the second bending direction D213, the positions of the tips of the plurality of second bending portions 21AY3 are matched with each other, the maximum thickness T3 is less likely to increase. Therefore, since the non-element space volume is less likely to decrease, the element space volume is more likely to increase, so that a higher effect can be obtained.

The actions and effects based on the configuration of the positive electrode 21 described here can be similarly obtained based on the configuration of the negative electrode 22 as well. That is, if the positions of the tips of the second bent portions 22AY3 gradually recede in the direction opposite to the second bent direction D223, the maximum thickness T4 is less likely to increase, thereby obtaining a higher effect. be able to.

Further, if the positive electrode tabs 30 are connected to each of the first bent portion 21AY2 and the second bent portion 21AY3, the positive electrode tabs 30 can be used to easily and stably connect the plurality of positive electrode current collectors 21A (lead-out portions 21AY). , a higher effect can be obtained.

The actions and effects based on the configuration of the positive electrode tab 30 described here can be similarly obtained based on the configuration of the negative electrode tab 40 as well. That is, if the negative electrode tabs 40 are connected to each of the first bent portion 22AY2 and the second bent portion 22AY3, the negative electrode tabs 40 can be used to easily and stably connect the plurality of negative electrode current collectors 22A (lead-out portions 22AY). , a higher effect can be obtained.

Further, if the bending direction (first bending direction D212) of each of the plurality of lead-out portions 21AY is a direction away from the outer cup 12 (negative terminal), the lead-out portion 21AY having positive polarity and negative polarity are connected. Since a short circuit with the external cup 12 is prevented, a higher effect can be obtained.

The actions and effects based on the configuration of the plurality of lead-out portions 21AY described here can also be similarly obtained based on the configuration of the plurality of lead-out portions 22AY. That is, if the bending direction (first bending direction D222) of each of the lead-out portions 22AY is the direction away from the outer can 11 (positive electrode terminal), the lead-out portion 22AY having the negative polarity and the lead-out portion 22AY having the negative polarity Since a short circuit with the outer can 11 is prevented, a higher effect can be obtained.

Further, if the lead-out direction D211 of each of the plurality of positive electrodes 21 (plural lead-out portions 21AY) and the lead-out direction D221 of each of the plurality of negative electrodes 22 (plural lead-out portions 22AY) are the same direction, two Since the secondary battery can be easily connected to an electronic device through the positive electrode 21 and the negative electrode 22, a higher effect can be obtained.

In addition, if the secondary battery has a flat and columnar battery can 10, that is, if the secondary battery is a button-type secondary battery, the size of a small secondary battery, which is greatly restricted in terms of size, can be reduced per unit volume. Since the energy density is effectively increased, a higher effect can be obtained.

<2. Secondary Battery (Second Embodiment)>
Next, a secondary battery according to a second embodiment of the present technology will be described.

<2-1. Configuration>
In the secondary battery of the present embodiment, unlike the secondary battery of the first embodiment in which the positive electrode tab 30 and the negative electrode tab 40 are used to collect current in the plurality of lead-out portions 21AY and 22AY, the plurality of lead-out portions In order to collect currents 21AY and 22AY, some of the plurality of positive electrode current collectors 21A (uppermost positive electrode current collector 21A described later) and some of the plurality of negative electrode current collectors 22A (described later) The lowermost negative electrode current collector 22A) is used.

The secondary battery of this embodiment has the same configuration as that of the secondary battery of the first embodiment, except for the following description.

FIG. 9 shows a perspective configuration of the secondary battery of this embodiment, and corresponds to FIG. 10 and 11 each show a cross-sectional configuration of the main part of the secondary battery of this embodiment. However, FIG. 10 corresponds to FIG. 3 and FIG. 11 corresponds to FIG. In each of FIGS. 9 to 11, the same reference numerals are assigned to the same components as those described in the first embodiment.

FIG. 10 shows a state in which the lowermost lead-out portion 21AY is separated from the other lead-out portions 21AY in order to make it easier to see the connection form of the lowermost lead-out portion 21AY. In order to make the connection format of the lead-out portion 22AY easier to see, the uppermost lead-out portion 22AY is shown separated from the other lead-out portions 22AY.

This secondary battery includes insulating layers 51 and 52 instead of the positive electrode tab 30 and the negative electrode tab 40, as shown in FIGS. In the battery element 20, a plurality of positive electrodes 21 and a plurality of negative electrodes 22 are alternately laminated with separators 23 interposed therebetween, with the positive electrodes 21 being the uppermost layer and the negative electrodes 22 being the lowermost layer.

(positive electrode)
The positive electrode 21 in the uppermost layer among the plurality of positive electrodes 21, that is, the positive electrode 21 closest to the outer can 11 among the plurality of positive electrodes 21 stacked together in the stacking direction S is an additional electrode as shown in FIG. is. The uppermost layer positive electrode 21 includes a positive electrode current collector 21A (hereinafter referred to as "uppermost layer positive electrode current collector 21A") led out in the lead-out direction D211 (right direction). The current collector 21A is an additional current collector that also serves as the positive electrode tab 30 .

In each of the plurality of positive electrodes 21 other than the uppermost positive electrode 21, the positive electrode current collector 21A is led out in the lead-out direction D211 (right direction) intersecting the stacking direction S, and the non-lead-out part 21AX and the lead-out part 21AX A part 21AY is included. The lead-out portion 21AY led out in the lead-out direction D211 is bent in the first bending direction D212 on the way. Here, the lead-out portion 21AY is bent in a direction (downward) away from the uppermost positive electrode 21 . That is, the bending direction (first bending direction D212) of lead-out portion 21AY is opposite to the bending direction (first bending direction D212) of lead-out portion 21AY in the first embodiment. When attempting to bend lead-out portion 21AY in a direction approaching outer can 11, there is no space in that direction for arranging first bent portion 21AY2, so lead-out portion 21AY has to be bent in the opposite direction. because you can't.

Since each of the plurality of lead-out portions 21AY bent in the first bending direction D212 is in contact with the adjacent (front) lead-out portion 21AY in the first bending direction D212 while overlapping, the adjacent lead-out portion 21AY It is connected.

Here, among the plurality of lead-out portions 21AY, some of the lead-out portions 21AY positioned on the rear side in the first bending direction D212 are bent in one step, and therefore, during bending in the first bending direction D212, terminated. Therefore, some lead-out portions 21AY include non-bending portions 21AY1 and first bending portions 21AY2. The non-bending portion 21AY1 extends in the lead-out direction D211. The first bending portion 21AY2 extends in the first bending direction D212.

Here, five positive electrodes 21 (excluding the uppermost positive electrode 21) and five negative electrodes 22 (excluding the lowermost negative electrode 22) are alternately stacked with the separators 23 interposed therebetween. Two lead-out portions 21AY located on the rear side in one bending direction D212 are bent in one step. Also, the positions of the tips of the two first bending portions 21AY2 are gradually retreated in the direction opposite to the first bending direction D212.

On the other hand, among the plurality of lead-out portions 21AY, the remaining lead-out portions 21AY located on the front side in the first bending direction D212 are bent in two stages, so that the non-bending portion 21AY1, the first bending portion 21AY2 and the second bending portion 21AY2 are bent in two stages. It includes a bent portion 21AY3. The second bending portion 21AY3 extends in the second bending direction D213.

Here, five positive electrodes 21 (excluding the uppermost positive electrode 21) and five negative electrodes 22 (excluding the lowermost negative electrode 22) are alternately stacked with the separators 23 interposed therebetween. Three lead-out portions 21AY located on the front side in one bending direction D212 are bent in two stages. Also, the positions of the tips of the three second bent portions 21AY3 are gradually retreated in the direction opposite to the second bent direction D213.

In the uppermost positive electrode 21, the positive electrode active material layer 21B is provided only on one side of the uppermost positive electrode current collector 21A. 21AX) are exposed. However, since the positive electrode active material layer 21B is provided on both sides of the uppermost positive electrode current collector 21A, the uppermost positive electrode current collector 21A (non-leading-out portion 21AX) is exposed on the side closer to the outer can 11. It doesn't have to be.

The end (leading-out portion 21AY) of the uppermost positive electrode current collector 21A is bent in two stages, and thus includes a non-bent portion 21AY1, a first bent portion 21AY2 and a second bent portion 21AY3. The first bent portion 21AY2 and the second bent portion 21AY3 are additional bent portions. As a result, the uppermost positive electrode current collector 21A is connected to the remaining lead-out portions 21AY (the second bent portion 21AY3 of the lead-out portions 21AY bent in two stages) among the plurality of lead-out portions 21AY. It is connected to a part of the plurality of lead-out portions 21AY (the first bent portion 21AY2 of the lead-out portions 21AY bent in one step).

On the other hand, the uppermost positive electrode current collector 21A is connected to the outer can 11 (bottom portion 11M) at the non-lead-out portion 21AX and the lead-out portion 21AY (non-bending portion 21AY1). As a result, the outer can 11 is connected to the other positive electrode 21 (positive electrode current collector 21A) via the uppermost positive electrode current collector 21A, which also serves as the positive electrode tab 30, and thus functions as a positive electrode terminal.

The thickness of the uppermost positive electrode current collector 21A that also serves as the positive electrode tab 30 is not particularly limited. In particular, the thickness of the uppermost positive electrode current collector 21A is preferably greater than the thickness of each of the plurality of other positive electrode current collectors 21A that do not also serve as the positive electrode tab 30 . This is because the electrical resistance of the uppermost positive electrode current collector 21A is reduced, so that the current collecting performance of the uppermost positive electrode current collector 21A is improved.

(negative electrode)
The multiple negative electrodes 22 have the same configuration as the multiple positive electrodes 21 described above. That is, among the plurality of negative electrodes 22, the lowest layer negative electrode 22, that is, the negative electrode 22 closest to the exterior cup 12 among the plurality of negative electrodes 22 stacked in the stacking direction S, is, as shown in FIG. Another additional electrode. The lowermost negative electrode 22 includes a negative electrode current collector 22A (hereinafter referred to as the “lowermost negative electrode current collector 22A”) led out in the lead-out direction D221 (right direction). The current collector 22A is another additional current collector that also serves as the negative electrode tab 40 .

In each of the plurality of negative electrodes 22 other than the lowermost negative electrode 22, the negative electrode current collector 22A is led out in the lead-out direction D221 (right direction) intersecting the stacking direction S, and the non-lead-out portion 22AX and the lead-out portion 22AX A part 22AY is included. The lead-out portion 22AY led out in the lead-out direction D221 is bent in the first bending direction D222 on the way. Here, the lead-out portion 22AY is bent in a direction (upward) away from the negative electrode 22 in the lowest layer. That is, the bending direction (first bending direction D222) of lead-out portion 22AY is opposite to the bending direction (first bending direction D222) of lead-out portion 22AY in the first embodiment. When attempting to bend the lead-out portion 22AY in a direction approaching the exterior cup 12, there is no space in that direction for arranging the first bent portion 22AY2, so the lead-out portion 22AY has to be bent in the opposite direction. because you can't.

Since each of the plurality of lead-out portions 22AY bent in the first bending direction D222 is in contact with the adjacent (front) lead-out portion 22AY in the first bending direction D222 while overlapping, the adjacent lead-out portion 22AY It is connected.

Here, among the plurality of lead-out portions 22AY, some of the lead-out portions 22AY positioned on the rear side in the first bending direction D222 are bent in one step, and therefore, during bending in the first bending direction D222, terminated. Therefore, some lead-out portions 22AY include non-bending portions 22AY1 and first bending portions 22AY2. The non-bending portion 22AY1 extends in the lead-out direction D221. The first bending portion 22AY2 extends in the first bending direction D222.

Here, five positive electrodes 21 (excluding the uppermost positive electrode 21) and five negative electrodes 22 (excluding the lowermost negative electrode 22) are alternately stacked with the separators 23 interposed therebetween. Two lead-out portions 22AY located on the rear side in one bending direction D222 are bent in one step. Also, the positions of the tips of the two first bending portions 22AY2 are gradually retreated in the direction opposite to the first bending direction D212.

On the other hand, among the plurality of lead-out portions 22AY, the remaining lead-out portions 22AY located on the front side in the first bending direction D222 are bent in two stages, so that the non-bent portion 22AY1, the first bent portion 22AY2 and the second bent portion 22AY2 are bent in two stages. It includes a bent portion 22AY3. The second bending portion 22AY3 extends in the second bending direction D223.

Here, five positive electrodes 21 (excluding the uppermost positive electrode 21) and five negative electrodes 22 (excluding the lowermost negative electrode 22) are alternately stacked with the separators 23 interposed therebetween. Three lead-out portions 22AY located on the front side in one bending direction D222 are bent in one step. Also, the positions of the tips of the three second bent portions 22AY3 are gradually retreated in the direction opposite to the second bent direction D223.

In the lowermost negative electrode layer 22, the negative electrode active material layer 22B is provided only on one side of the lowermost negative electrode current collector 22A. 22AX) are exposed. However, since the negative electrode active material layer 22B is provided on both surfaces of the lowermost negative electrode current collector 22A, the lowermost negative electrode current collector 22A (non-derivation portion 22AX) is exposed on the side closer to the outer cup 12. It doesn't have to be.

The end portion (leading-out portion 22AY) of the lowermost negative electrode current collector 22A is bent in two stages, and thus includes a non-bent portion 22AY1, a first bent portion 22AY2 and a second bent portion 22AY3. The first bent portion 22AY2 and the second bent portion 22AY3 are other additional bent portions. As a result, the lowermost negative electrode current collector 22A is connected to the remaining lead-out portions 22AY (the second bent portion 22AY3 of the lead-out portions 22AY bent in two stages) among the plurality of lead-out portions 22AY. It is connected to a part of the plurality of lead-out portions 22AY (the first bent portion 22AY2 of the lead-out portions 22AY bent in one step).

On the other hand, the lowermost negative electrode current collector 22A is connected to the exterior cup 12 (bottom portion 12M) at the non-derivation portion 22AX and the derivation portion 22AY (non-bending portion 22AY1). Thus, the outer cup 12 is connected to the other negative electrode 22 (negative electrode current collector 22A) via the lowermost negative electrode current collector 22A, which also serves as the negative electrode tab 40, and thus functions as a negative electrode terminal.

The thickness of the lowermost negative electrode current collector 22A, which also serves as the negative electrode tab 40, is not particularly limited. In particular, the thickness of the lowermost negative electrode current collector 22A is preferably greater than the thickness of each of the plurality of other negative electrode current collectors 22A that do not also serve as the negative electrode tab 40 . This is because the electrical resistance of the lowermost negative electrode current collector 22A is reduced, so that the current collecting performance of the lowermost negative electrode current collector 22A is improved.

(insulating layer)
The insulating layer 51 is arranged between the outer cup 12 and the uppermost positive electrode current collector 21A (second bent portion 21AY3), which also serves as the positive electrode tab 30. to prevent short circuits with The insulating layer 52 is arranged between the lowermost negative electrode current collector 22A (second bent portion 22AY3), which also serves as the negative electrode tab 40, and the outer can 11. The second bent portion 22AY3 and the outer can 11 to prevent short circuits with Each of the insulating layers 51 and 52 is an insulating resin tape, and the resin tape is made of one or two insulating materials such as polymer materials such as polyimide, polyethylene terephthalate (PET) and polyolefin. contains more than one type.

<2-2. Operation>
The operation (charging/discharging operation) of the secondary battery of this embodiment is the same as the operation of the secondary battery of the first embodiment. During charging and discharging, the uppermost positive electrode current collector 21A also serves as the positive electrode tab 30, so that the uppermost positive electrode current collector 21A is used to collect current from a plurality of other positive electrode current collectors 21A. Since the lowermost negative electrode current collector 22A also serves as the negative electrode tab 40, the lowermost negative electrode current collector 22A is used to collect current from a plurality of other negative electrode current collectors 22A.

<2-3. Manufacturing method>
The method for manufacturing the secondary battery of this embodiment is the same as the method for manufacturing the secondary battery of the first embodiment, except for the following description.

When fabricating the positive electrode 21, the bending directions of the plurality of positive electrode current collectors 21A (lead-out portions 21AY) other than the uppermost positive electrode current collector 21A are changed to opposite directions, and the uppermost positive electrode current collector 21A (lead-out portion 21AY) is bent in two stages in the same direction. Further, in the uppermost positive electrode 21, the positive electrode active material layer 21B is formed only on one side of the positive electrode current collector 21A. Further, the uppermost positive electrode current collector 21A is connected to a plurality of other positive electrode current collectors 21A.

When fabricating the negative electrode 22, the bend directions of the plurality of negative electrode current collectors 22A (leading portions 22AY) other than the lowermost negative electrode current collector 22A are changed to opposite directions, and the lowermost negative electrode current collector 22A (lead-out portion 22AY) is bent in two stages in the same direction. In the lowermost negative electrode 22, the negative electrode active material layer 22B is formed only on one side of the negative electrode current collector 22A. Further, the lowermost negative electrode current collector 22A is connected to a plurality of other negative electrode current collectors 22A.

When assembling the secondary battery, the uppermost positive electrode current collector 21A is joined to the outer can 11 and the lowermost negative electrode current collector 22A is joined to the outer cup 12 .

<2-4. Action and effect>
According to the secondary battery of this embodiment, instead of the positive electrode tab 30, the uppermost positive electrode current collector 21A is connected to a plurality of other positive electrode current collectors 21A, and instead of the negative electrode tab 40, the lowermost layer has the same configuration as the configuration of the secondary battery of the first embodiment, except that the negative electrode current collector 22A is connected to a plurality of other negative electrode current collectors 22A.

In this case, for the same reason as described for the secondary battery of the first embodiment, the maximum thickness T1 is smaller than the maximum thickness T11 and the maximum Thickness T2 is smaller than maximum thickness T12. As a result, the volume of the non-element space is reduced, so the volume of the element space is increased. Therefore, the energy density per unit volume can be increased.

Further, when the maximum thickness T3 is smaller than the maximum thickness T13 and the maximum thickness T4 is smaller than the maximum thickness T14, the volume of the non-element space is further decreased and the volume of the element space is further increased. , the energy density per unit volume can be further increased.

Moreover, when the uppermost positive electrode current collector 21A is connected to a plurality of other positive electrode current collectors 21A, the uppermost positive electrode current collector 21A also serves as the positive electrode tab 30 and the lowermost negative electrode current collector 21A. When the current collector 22A is connected to a plurality of other negative electrode current collectors 22A, the lowermost negative electrode current collector 22A also serves as the negative electrode tab 40 . Therefore, even if the positive electrode tab 30 and the negative electrode tab 40 are not newly used, each of the plurality of positive electrode current collectors 21A and the plurality of negative electrode current collectors 22A can collect current, so that a higher effect can be obtained.

In particular, if the bending direction (first bending direction D212) of each of the plurality of lead-out portions 21AY is a direction away from the uppermost positive electrode current collector 21A, a space for arranging the plurality of first bending portions 21AY2 is secured. . Therefore, since each of the plurality of lead-out portions 21AY can be easily and stably bent, a higher effect can be obtained.

The actions and effects based on the configuration of the plurality of lead-out portions 21AY described here can also be similarly obtained based on the configuration of the plurality of lead-out portions 22AY. That is, if the bending direction (first bending direction D222) of each of the plurality of lead-out portions 22AY is the direction away from the lowermost negative electrode current collector 22A, each of the plurality of lead-out portions 22AY can be easily and stably bent. Therefore, a higher effect can be obtained.

Further, if the uppermost positive electrode current collector 21A is exposed, the uppermost positive electrode current collector 21A can be easily connected to the outer can 11, so that a higher effect can be obtained. In this case, since the positive electrode active material layer 21B is not interposed between the uppermost positive electrode current collector 21A and the outer can 11, electrical conduction between the uppermost positive electrode current collector 21A and the outer can 11 is low. can improve sexuality.

The actions and effects based on the configuration of the uppermost positive electrode current collector 21A described here can be similarly obtained based on the configuration of the lowermost negative electrode current collector 22A. That is, if the lowermost negative electrode current collector 22A is exposed, the lowermost negative electrode current collector 22A can be easily connected to the outer cup 12, so that a higher effect can be obtained. Of course, the electrical conductivity between the lowermost negative electrode current collector 22A and the exterior cup 12 can also be improved.

<3. Comparison of element space volume>
Here, logically (mathematically) the element space volume (mm ³ ) for each of the secondary battery of the first embodiment (FIGS. 1 to 4) and the secondary battery of the comparative example (FIGS. 7 and 8) is By calculating and comparing their element space volumes with each other, the results shown in Table 1 are obtained.

The column of "Construction" shown in Table 1 indicates the type of secondary battery. That is, "comparative" indicates the secondary battery of the comparative example, and "implementation" indicates the secondary battery of the first embodiment.

The conditions for calculating the element space volume are as follows. Various dimensions of the battery element 20, that is, the number of layers of the positive electrode 21, the number of layers of the negative electrode 22, the thickness (μm) of the positive electrode current collector 21A, the maximum overlapping thickness (μm) of the plurality of positive electrode current collectors 21A, and the negative electrode collector Table 1 shows the thickness (μm) of the current collector 22A and the maximum overlapping thickness (μm) of the plurality of negative electrode current collectors 22A. Here, since the maximum thicknesses T1, T2, T11, and T12 are focused on as parameters that affect the device space volume, the maximum overlapping thicknesses of the plurality of positive electrode current collectors 21A are the maximum thicknesses T1 and T11. In addition, the maximum overlapping thicknesses of the plurality of negative electrode current collectors 22A are the maximum thicknesses T2 and T12. That is, for convenience, the thickness of the positive electrode tab 30 and the thickness of the negative electrode tab 40 are not considered here.

Since the three-dimensional shape of the battery can 10 is flat and substantially cylindrical with the side wall portion M3 (tapered surface M3T), the battery can 10 has a substantially cylindrical internal space capable of accommodating the battery element 20. are doing. As various dimensions of the battery can 10, the outer diameter D = 12.1 mm, the height H = 4.0 mm (the number of layers of the positive electrode 21 = the number of layers of the negative electrode 22 = 15) or the outer diameter D = 12.1 mm, the height H=5.4 mm (the number of layers of positive electrode 21=20 and the number of layers of negative electrode 22=20). Moreover, the notch distance for the tapered surface M3T is 1.8 mm.

When calculating the element space volume, first, based on the outer diameter D and height H of the battery can 10, the maximum volume (space volume (mm ³ )). For the sake of convenience, the thickness (thickness) of the battery can 10 is not taken into consideration when calculating the spatial volume. Subsequently, the number of layers of the positive electrode 21, the number of layers of the negative electrode 22, the thickness of the positive electrode current collector 21A, the maximum overlapping thickness of the plurality of positive electrode current collectors 21A, the thickness of the negative electrode current collector 22A and the plurality of negative electrode collectors The non-element space volume (mm ³ ) is calculated based on the maximum overlapping thickness of the conductor 22A. Finally, the element spatial volume is calculated by subtracting the non-element spatial volume from the spatial volume. This element space volume corresponds to the area of the planar shape of the negative electrode 22 (excluding the portion where the negative electrode current collectors 22A overlap each other)×the height of the battery element 20 . In Table 1, as described above, by changing the height H of the battery can 10 in two ways, the number of layers of the positive electrode 21 and the number of layers of the negative electrode 22 are also changed in two ways.

Table 1 also shows the battery capacity (mAh) in order to make it easier to understand the influence caused by the difference in the element space volume. This battery capacity is the battery capacity obtained when the area of each of the positive electrode 21 and the negative electrode 22 is increased to the maximum without changing the number of layers of each of the positive electrode 21 and the negative electrode 22 .

As shown in Table 1, the element space volume varies depending on the configuration of the secondary battery. Specifically, in the secondary battery of the comparative example, the maximum overlapping thickness of the plurality of positive electrode current collectors 21A and the maximum overlapping thickness of the plurality of negative electrode current collectors 22A are significantly increased. Since the element space volume increases, the element space volume decreases. On the other hand, in the secondary battery of the present embodiment, the maximum overlapping thickness of the plurality of positive electrode current collectors 21A and the maximum overlapping thickness of the plurality of negative electrode current collectors 22A are greater than the secondary battery of the comparative example. are greatly reduced, the non-element space volume decreases, and the element space volume increases.

From the results shown in Table 1, in the secondary battery of the present embodiment, the current collection type of each of the plurality of positive electrode current collectors 21A and the plurality of negative electrode current collectors 22A is higher than that of the secondary battery of the comparative example. Since the non-element space volume is reduced from the point of view, the element space volume is increased. This increases the energy density per unit volume.

<4. Variation>
Next, a modification of the secondary battery described above will be described. The configuration of the secondary battery can be changed as appropriate, as described below. However, any two or more of the series of modifications described below may be combined with each other.

[Modification 1]
In the first embodiment (FIGS. 3 and 4), the rest of the plurality of lead-out portions 21AY include the second bent portion 21AY3, and the rest of the plurality of lead-out portions 22AY form the second bent portion 22AY3. contains.

However, the rest of the plurality of lead-out portions 21AY may not include the second bent portion 21AY3, and the rest of the plurality of lead-out portions 22AY may not include the second bent portion 22AY3. good too. Of course, while the rest of the plurality of lead-out portions 21AY include the second bent portion 21AY3, the rest of the plurality of lead-out portions 22AY do not need to include the second bent portion 22AY3. While the rest of the plurality of lead-out portions 21AY do not include the second bent portion 21AY3, the rest of the plurality of lead-out portions 22AY may include the second bent portion 22AY3.

In these cases, as described above, since the maximum thicknesses T1 and T2 are smaller than the maximum thicknesses T11 and T12, respectively, the element space volume increases, so that similar effects can be obtained. be able to. However, in order to increase the current collection area as much as possible and increase the element space volume as much as possible, a plurality of It is preferable that the rest of the lead-out portions 21AY include the second bent portion 21AY3, and the rest of the plurality of lead-out portions 22AY include the second bent portion 22AY3.

Although not specifically illustrated here, Modification 1 described here may be applied to the second embodiment (FIGS. 10 and 11). Also in this case, since the maximum thicknesses T1 and T2 are each smaller than the maximum thicknesses T11 and T12, the same effect can be obtained.

[Modification 2]
In the first embodiment (FIG. 2), the battery element 20 has one tapered surface M3T, and each of the plurality of lead-out portions 21AY and 22AY is arranged on the side wall portion M3 (tapered surface M3T). As a result, the lead-out portions 21AY and 22AY are arranged adjacent to each other, so that the tab portion 30B of the positive electrode tab 30 and the tab portion 40B of the negative electrode tab 40 are arranged adjacent to each other. In this case, lead-out direction D211 of positive electrode 21 (plural lead-out portions 21AY) and lead-out direction D221 of negative electrode 22 (plural lead-out portions 22AY) are common to each other.

However, as shown in FIG. 12 corresponding to FIG. 2, the battery element 20 has two tapered surfaces M3T arranged opposite to each other, and the plurality of lead-out portions 21AY are located on one side wall portion M3 ( (tapered surface M3T) and a plurality of lead-out portions 22AY may be disposed on the other side wall portion M3 (tapered surface M3T). As a result, the lead-out portions 21AY and 22AY are arranged opposite to each other, so that the tab portion 30B of the positive electrode tab 30 and the tab portion 40B of the negative electrode tab 40 may be arranged on opposite sides. In this case, the lead-out direction D211 of the positive electrode 21 (the plurality of lead-out portions 21AY) and the lead-out direction D221 of the negative electrode 22 (the plurality of lead-out portions 22AY) are opposite to each other.

In this case also, the positive electrode tab 30 can collect current from the plurality of lead-out portions 21AY, and the negative electrode tab 40 can collect current from the plurality of lead-out portions 22AY, so that similar effects can be obtained. In this case, the fact that the positive electrode tab 30 and the negative electrode tab 40 are positioned opposite to each other can be used to increase the degree of freedom regarding the type of connection of the secondary battery to the electronic device.

Although not specifically illustrated here, Modification 2 described here may be applied to the second embodiment (FIG. 9). That is, the uppermost positive electrode current collector 21A (lead-out portion 21AY) that also serves as the positive electrode tab 30 is arranged on one side wall portion M3 (tapered surface M3T), and the lowermost layer that also serves as the negative electrode tab 40 is arranged. The negative electrode current collector 22A (lead-out portion 22AY) may be arranged on the other side wall portion M3 (tapered surface M3T). Similar effects can be obtained in this case as well.

[Modification 3]
In the first embodiment (FIGS. 1 and 2), the positive electrode tab 30 includes a substantially circular tab portion 30A and a strip-shaped tab portion 30B, and the negative electrode tab 40 includes a substantially circular tab portion 40A and a strip-shaped tab portion 30B. It includes a shaped tab portion 40B. However, the configuration of each of the positive electrode tab 30 and the negative electrode tab 40 is not particularly limited as long as it can collect current from a plurality of positive electrode current collectors 21A and can collect current from a plurality of negative electrode current collectors 22A.

Specifically, as shown in FIG. 13 corresponding to FIG. 1 and FIG. 14 corresponding to FIG. 2, the positive electrode tab 30 includes a strip-shaped tab portion 30C instead of the substantially circular tab portion 30A. In addition, the negative electrode tab 40 may include a strip-shaped tab portion 40C instead of the substantially circular tab portion 40A.

Tab portion 30</b>C extends away from battery element 20 . Therefore, the positive electrode tab 30 has a three-dimensional shape that is bent halfway in the direction away from the battery element 20 . The bending angle of the positive electrode tab 30 (the angle defined by the tab portions 30B and 30C) is not particularly limited, but may be 90° or the like.

The tab portion 40C has a configuration similar to that of the tab portion 30C described above. That is, tab portion 40</b>C extends away from battery element 20 . Therefore, the negative electrode tab 40 has a three-dimensional shape that is bent halfway in the direction away from the battery element 20 . The bending angle of the negative electrode tab 40 (the angle defined by the tab portions 40B and 40C) is not particularly limited, but may be 90° or the like.

Since the positive electrode tab 30 is connected to the outer can 11 at the tab portion 30C, the outer can 11 functions as a positive electrode terminal. Since the negative tab 40 is connected to the outer cup 12 at the tab 40 portion C, the outer cup 12 functions as a negative terminal.

In this case also, the positive electrode tab 30 can collect current from the plurality of lead-out portions 21AY, and the negative electrode tab 40 can collect current from the plurality of lead-out portions 22AY, so that similar effects can be obtained.

However, when the strip-shaped tab portion 30C having a small area is used, the contact area between the tab portion 30C and the outer can 11 is reduced, so the electrical resistance of the positive electrode tab 30 may increase. . Therefore, in order to reduce the electric resistance of the positive electrode tab 30 as much as possible, the positive electrode tab 30 preferably includes a substantially circular large-area tab portion 30A. This is because the electrical resistance of the positive electrode tab 30 is reduced because the contact area between the tab portion 30A and the outer can 11 is increased.

The actions and effects based on the configuration of the positive electrode tab 30 (tab portion 30C) described here can also be similarly obtained based on the configuration of the negative electrode tab 40 (tab portion 40C). That is, it is preferable that the negative electrode tab 40 includes the tab portion 40A in order to obtain the same effect even if the negative electrode tab 40 includes the tab portion 40C and to reduce the electrical resistance thereof.

When the tab portions 30C and 40C are used, an extra space 10J is required inside the battery can 10 for arranging the tab portions 30C and 40C as shown in FIG. Since this surplus space 10J is a space (non-element space) in which the battery element 20 cannot be arranged, it causes a decrease in element space volume. On the other hand, when the tab portions 30A and 30B are used, as shown in FIG. 1, the surplus space 10J is hardly generated, so the element space volume increases. Therefore, in order to increase the element space volume, it is preferable to use the tab portions 30A and 30B rather than the tab portions 30C and 40C.

Of course, although not specifically illustrated here, the positive electrode tab 30 including the tab portion 30A and the negative electrode tab 40 including the tab portion 40C may be used in combination, or the positive electrode tab 30 including the tab portion 30C and the tab portion 40A may be used in combination. may be used in combination with the negative electrode tab 40 containing. Similar effects can be obtained in these cases as well.

[Modification 4]
In the manufacturing process of the secondary battery, the laminated body 120 is housed inside the outer can 11, and the outer can 11 and the outer cup 12 (side wall portions 11W, 12S) are crimped to each other, and then the battery can 10 is inserted through the injection hole. An electrolytic solution is injected into the interior of (the exterior can 11 and the exterior cup 12). That is, after the battery can 10 is formed, the electrolytic solution is injected into the inside of the battery can 10 to impregnate the laminate 120 with the electrolytic solution.

However, after housing the laminate 120 inside the outer can 11 and injecting the electrolytic solution into the outer can 11, the outer can 11 and the outer cup 12 may be crimped to each other. That is, before forming the battery can 10 , the electrolytic solution may be injected into the outer can 11 to impregnate the laminate 120 with the electrolytic solution. In this case, the battery can 10 does not have to be provided with an injection hole.

In this case as well, the battery element 20 is produced by impregnating the laminate 120 with the electrolytic solution, and the battery element 20 is sealed inside the battery can 10, so that similar effects can be obtained. In this case, it is not particularly necessary to provide an injection hole in the battery can 10, so the configuration of the battery can 10 can be simplified. In addition, since the electrolyte is injected into the outer can 11 through the opening having a larger opening area than the injection hole, the efficiency of injecting the electrolyte into the laminate 120 can be improved, and the injection of the electrolyte can be improved. The process can be simplified.

[Modification 5]
In the first embodiment (FIG. 1), the battery can 10 is a crimp-type battery can, but the type of the battery can 10 is not particularly limited.

Specifically, as shown in FIG. 15 corresponding to FIG. 1, a welded battery can 60 may be used instead of the crimped battery can 10 . This battery can 60 includes an exterior can 61 and an exterior lid 62 . A secondary battery using this battery can 60 has a configuration similar to that of the secondary battery shown in FIG.

The outer can 61 has the same configuration as the outer can 11 . That is, the outer can 61 has a bottom portion 61M, a side wall portion 61W, and an opening portion 61K, and accommodates the battery element 20 therein. Since the negative electrode tab 40 is connected to the outer can 61 (bottom portion 61M), the outer can 61 functions as a negative electrode terminal. Therefore, the material for forming the outer can 61 is the same as the material for forming the negative electrode tab 40 .

The exterior lid 62 is a plate-like member that seals the opening 61K of the exterior can 61, and is joined to the exterior can 61 using a welding method or the like. As a result, the exterior lid 62 is firmly connected to the exterior can 61 , so that the exterior lid 62 after joining cannot be separated from the exterior can 61 . The exterior lid 62 has a through hole 60K, and an electrode terminal 70 is attached to the through hole 60K via a gasket 80. As shown in FIG.

Since the positive electrode tab 30 is connected to the electrode terminal 70, the electrode terminal 70 functions as a positive electrode terminal. Therefore, the material for forming the electrode terminal 70 is the same as the material for forming the positive electrode tab 30 . The electrode terminal 70 extends from the inside of the battery can 60 to the outside of the battery can 60 via the through hole 60K, and has a substantially cylindrical shape whose outer diameter is locally reduced inside the through hole 60K. It has a three-dimensional shape. However, the electrode terminal 70 may have another three-dimensional shape such as a substantially polygonal prism. Gasket 80 is arranged between battery can 60 and electrode terminal 70 and contains one or more of insulating materials such as polypropylene and polyethylene.

In the manufacturing process of the secondary battery using the welded battery can 60, the laminated body 120 is housed inside the outer can 61, and the outer cover 62 is joined to the outer can 61 by welding or the like. The electrolytic solution may be injected into the interior of the battery can 60 (the exterior can 61 and the exterior lid 62) through the liquid injection hole. That is, after the battery can 60 is formed (after the exterior lid 62 is joined to the exterior can 61), the electrolyte may be injected into the interior of the battery can 60 to impregnate the laminate 120 with the electrolyte.

Alternatively, the laminated body 120 may be housed inside the outer can 61, and the outer can 61 may be joined to the outer cover 62 by welding or the like after the electrolytic solution is injected into the outer can 61. That is, before the battery can 60 is formed (before the exterior lid 62 is joined to the exterior can 61), the electrolyte may be injected into the interior of the exterior can 61 to impregnate the laminate 120 with the electrolyte. In this case, the battery can 60 does not have to be provided with an injection hole.

Also in this case, since the energy density per volume increases as the element space volume increases, a similar effect can be obtained. In this case, compared with the case of using the crimp-type battery can 10, the element space volume is increased by the amount corresponding to the absence of the crimp portion C, so that a higher effect can be obtained.

When the welded battery can 60 is used, part of the electrode terminal 70 enters the inside of the battery can 60, so that the space volume of the element is increased by the height of the part of the electrode terminal 70. Decrease. However, the amount of reduction in the element space volume due to the portion of the electrode terminal 70 is sufficiently smaller than the amount of reduction in the element space volume due to the presence of the crimp portion C. FIG. Therefore, when the welded battery can 60 is used, compared with the case where the crimped battery can 10 is used, the element space volume is increased, so that a higher effect can be obtained.

In particular, if the electrolytic solution is injected into the exterior can 61 before the battery can 60 is formed, there is no need to provide an injection hole in the battery can 60, so the configuration of the battery can 60 can be simplified. . In addition, since the electrolyte is injected into the exterior can 61 through the opening having a larger opening area than the injection hole, the efficiency of injecting the electrolyte into the laminate 120 can be improved, and the injection of the electrolyte can be improved. The process can be simplified.

Although not specifically illustrated here, Modification 4 described here may be applied to the second embodiment. That is, when the uppermost positive electrode collector 21A serves as the positive electrode tab 30 and the lowermost negative electrode collector 22A serves as the negative electrode tab 40, the welded battery can 60 may be used. A similar effect can be obtained.

[Modification 6]
Even when the welded battery can 60 described above is used, the configuration of each of the positive electrode tab 30 and the negative electrode tab 40 is not particularly limited as described in the third modification.

Specifically, as shown in FIG. 16 corresponding to FIG. 15 and FIG. 17 corresponding to FIG. 2, the positive electrode tab 30 including the tab portion 30C and the negative electrode tab 40 including the tab portion 40A may be combined with each other. . In this case, the attachment position of the electrode terminal 70 to the battery can 60 may be changed according to the combination of the positive electrode tab 30 and the negative electrode tab 40 described above.

Here, since the battery can 60 has the through hole 60K in the outer can 61 (side wall portion 61W) instead of the outer lid 62 (bottom portion 62M), the electrode terminal 70 is provided in the side wall portion 61W. It is attached via a gasket 80 to the through hole 60K.

Since the positive electrode tab 30 includes the tab portions 30B and 30C as described above, the positive electrode tab 30 is bent in the middle. Here, the bending angle of the positive electrode tab 30 is less than 90°. Since the positive electrode tab 30 is thereby connected to the electrode terminal 70, the electrode terminal 70 functions as a positive electrode terminal.

Also in this case, since the energy density per volume increases as the element space volume increases, a similar effect can be obtained.

Although the present technology has been described above with reference to one embodiment and example, the configuration of the present technology is not limited to the configuration described in the one embodiment and example, and can be variously modified.

Specifically, the case where the electrode reactant is lithium has been described, but the electrode reactant is not particularly limited. Specifically, the electrode reactants may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium and calcium, as described above. Alternatively, the electrode reactant may be other light metals such as aluminum.

Since the effects described herein are merely examples, the effects of the present technology are not limited to the effects described herein. Accordingly, other advantages may be obtained with respect to the present technology.

Claims (14)

A power generation element including a plurality of electrodes stacked with each other with separators in the stacking direction,
each of the plurality of electrodes includes a current collector led out in a first direction intersecting with the stacking direction;
each end of the plurality of current collectors led out in the first direction includes a first bent portion bent in a second direction intersecting the first direction,
The first bending portion is in contact with the adjacent first bending portion in the second direction while overlapping,
at least one of the plurality of first bent portions terminates in the middle of the end surface of the power generation element in the second direction ;
each length of the plurality of current collectors is the same as each other,
secondary battery. Positions of respective tips of the plurality of first bent portions that terminate in the middle of the end face in the second direction gradually recede in a direction opposite to the second direction,
The secondary battery according to claim 1 . Some of the end portions of the plurality of current collectors led out in the first direction are further connected to the first bent portion and are arranged along the power generating element in the first direction. including a second bend bent in an opposite third direction,
The secondary battery according to claim 1 or 2 . the position of the tip of each of the plurality of second bends gradually recedes in the direction opposite to the third direction,
The secondary battery according to claim 3 . Furthermore, electrode wiring connected to each of the first bent portion and the second bent portion,
The secondary battery according to claim 3 or 4 . moreover,
An exterior member that houses the power generation element,
The exterior member includes a first exterior having one of positive polarity and negative polarity, and a positive polarity and a negative polarity facing the first exterior with the power generation element interposed therebetween in the stacking direction. a second exterior having the other of
each of the plurality of current collectors has a positive polarity or a negative polarity,
the second direction is a direction in which each of the plurality of current collectors moves away from the first exterior portion or the second exterior portion;
The first exterior part or the second exterior part has a polarity opposite to the polarity of each of the plurality of current collectors,
The secondary battery according to claim 5 . Further comprising an additional electrode stacked on top of the plurality of electrodes in the stacking direction with the separator interposed therebetween,
the additional electrode includes an additional current collector led out in the first direction;
The end portion of the additional current collector led out in the first direction includes an additional bent portion bent in the second direction and then bent in the third direction, and the first bent portion and the second connected to each of the flexures,
The secondary battery according to claim 3 or 4 . The second direction is a direction away from the additional electrode,
The secondary battery according to claim 7 . the additional current collector is exposed;
The secondary battery according to claim 7 or 8 . a plurality of positive electrodes, which are the plurality of electrodes;
10. The secondary battery according to any one of claims 1 to 9 , further comprising a plurality of negative electrodes that are said plurality of other electrodes. The first direction of each of the plurality of positive electrodes and the first direction of each of the plurality of negative electrodes are directions common to each other,
The secondary battery according to claim 10 . the first direction in each of the plurality of positive electrodes and the first direction in each of the plurality of negative electrodes are directions opposite to each other;
The secondary battery according to claim 10 . Furthermore, comprising a flat and columnar exterior member that houses the power generation element,
The secondary battery according to any one of claims 1 to 12 . A flat and columnar secondary battery,
The secondary battery according to any one of claims 1 to 13 .

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